Case study: Detecting intracranial hypertension using transcranial doppler ultrasound

Transcranial Doppler (TCD) ultrasound is a non-invasive tool utilized in point-of-care ultrasound (POCUS) for assessing cerebral blood flow dynamics. This case study explores the application of TCD in detecting intracranial hypertension in a clinical setting.

Case presentation:

• A 45-year-old male presented to the emergency department with severe headache, nausea, and blurred vision.
• Medical history included hypertension and a recent head trauma from a minor car accident.

Physical Examination:

• The patient was conscious but exhibited signs of increased intracranial pressure (ICP), such as papilledema and bradycardia.
• Initial neurological assessment showed no focal deficits.

Clinical Decision:

• Given the suspicion of intracranial hypertension, a TCD ultrasound was performed at the bedside to quickly assess cerebral blood flow dynamics and evaluate for raised ICP.

Indications for TCD

• Intracranial hypertension
• Suspected diagnosis of cerebral circulatory arrest
• Vasospasm detection
• Identification of midline shift

Essential Information on TCD

• TCD offers real-time information and can be performed at the bedside.
• It is not a replacement for CT scans but provides trending capabilities and immediate data.

Functional Anatomy and Machine Setup

Anatomy:

• Key structures include the circle of Willis and intracranial arteries.
• The mesencephalic plane is critical for vascular assessment.

Machine Setup:

• Transducer: Phased array
• Preset: Transcranial (or cardiac)
• Orientation: Index marker toward the frontal bone/orbital
• Depth: 15 cm

Patient Positioning:

• Patient positioned supine with the head of the bed elevated to 30 degrees.
• Landmarks include the ear and temporomandibular joint.
• Transducer placed 2-3 cm above the temporomandibular joint at the level of the temporal bone.

Scanning Plane:

• Mesencephalic plane: Visualizes the middle cerebral artery (MCA) with red flow toward the transducer. Use pulsed wave Doppler to measure cerebral blood flow velocities.

Assessment Using TCD

• Pulsatility Index (PI): Calculated using the formula:
  PI  = (PSV – EDV)/ MFV
  Where PSV is peak systolic velocity, EDV is end diastolic velocity, and MFV is mean flow velocity.

• A normal PI ranges from 0.5 to 1. A PI > 1.2 indicates increased ICP. The estimated ICP approximates PI x 10.

Findings:

• The patient’s PI was 1.4, suggesting raised ICP.
• Immediate intervention with measures to reduce ICP was initiated.

Conclusion

Transcranial Doppler is a valuable, non-invasive technique for assessing intracranial hypertension. By understanding cerebral anatomy and utilizing proper ultrasound techniques, healthcare providers can make rapid and accurate diagnoses, improving patient outcomes.

For more in-depth information on TCD and advanced applications, consider downloading NYSORA’s POCUS App for detailed resources, illustration, animations, and more.